NEW YORK, June 12 (Reuters) - JPMorgan Chase boosted its outlook for investment banking revenue, forecasting a jump of 25% to 30% in the second quarter fueled by capital markets, a top executive said on Wednesday.

The forecast became more bullish than in May, when the bank predicted investment banking revenue would rise by a mid-teens percentage in the second quarter.

"Capital markets continues to be extremely robust and the overall franchise has improved," said Troy Rohrbaugh, co-CEO of JPMorgan's commercial and investment bank.

Trading revenue is expected to improve slightly, exceeding the bank's earlier estimate for a percentage gain in the mid-single digits.

In the first quarter, JPMorgan's trading revenue fell 5% to $8 billion, with revenue from fixed income, currency and commodities dropping 7%, while equities was flat.

Meanwhile, investment banking revenue gained 27% to $2 billion in the first quarter, driven by higher fees for debt and stock underwriting.

JPMorgan's board has identified Rohrbaugh as a potential candidate to succeed CEO Jamie Dimon, who is expected to step down in less than five years.

The other contenders include Jennifer Piepszak, co-CEO of commercial and investment banking, Marianne Lake, CEO of consumer and community banking, and Mary Erdoes, CEO of asset and wealth management.

Rohrbaugh outlined leadership changes across the bank's Wall Street division, including his own promotion in January to run it alongside Piepszak.

"A lot of firms when they create co-heads, it turns into a cage match -- that's definitely not how JPMorgan works," Rohrbaugh said.

Given their respective backgrounds, Rohrbaugh typically focuses on markets, while Piepszak concentrates on investment banking, and they jointly manage payments.

"That said, if I'm on a plane, then everyone in markets will call Jenn (Piepszak) and she'll make the decision," Rohrbaugh said. "And Jamie will hold us jointly responsible for the outcome and anything that is truly strategic ... Jamie can get you anywhere."

Rohrbaugh, who traded currency options earlier in his career, said the Federal Reserve will probably delay interest rate cuts beyond market expectations.

The Fed held interest rates steady earlier Wednesday and pushed out the start of rate cuts to perhaps as late as December. (Reporting by Nupur Anand in New York and Manya Saini in Bengaluru; Editing by Lananh Nguyen and Daniel Wallis)